Powermac G3 BW Memory

Discussion in 'Mac Basics and Help' started by mhhack, Feb 22, 2006.

  1. mhhack macrumors newbie

    Feb 21, 2006

    I'm PC guy who just came into a Rev 1 Powermac G3, with a Sonnet G4 800mhz upgrade. Whe I got the machine it had 384mb of ram, to which I have attempted to add two 256mb sticks. I found that with all the four memory slots filled the machine would not boot, while any combination of three filled slots would work, with any combination of memory, all 256mb sticks or two 256mb sticks and one 128mb stick.

    This is certainly weird - does anyone have any idea about how to proceed?

  2. FoxyKaye macrumors 68000


    Jan 23, 2004
    San Francisco, Terre d'Ange, Bas Lag, Gallifrey
    There's a couple issues with the memory controller on the Rev. 1 B/W that are fairly unique.

    Some of these controllers will not accept high density RAM (16x32, I believe), but only the lower density (8x16) PC100 RAM. Double check that the RAM you're putting in is PC100 and not PC66 as well - this would cause boot problems. Two other issues I can think of are whether or not the RAM you're putting in is 2-2-2 that is both unbuffered and non-parity. Otherwise, it won't work either. Finally, some of the early memory controllers are so picky they won't accept PC133 RAM either, only PC100, but this is really really rare.

    Other World Computing has a good writeup on these issues, since I can't remember the RAM density numbers offhand - see the note at the very bottom of this page: http://eshop.macsales.com/item/Other World Computing/100SD256324/
  3. RGunner macrumors 6502a


    Jul 3, 2002
    Midnight Sun
    Mac Memory

    Remember, any old PC100 Ram may / may not be entirely compatible with Macs.

    G3 B&W's require 2 things to work correctly on the Ram department 1) they must have the correct SPD (which is the internal memory coding) and 2) they must be at least 8ns memory. I encourage you to go over to www.macgurus.com and read up on the memory timings interface.


    We have a G3 B&W here with 1GB of Memory in it, works perfectly.

    Also, download Dimm First aid *runs under OS 9.1 or 9.2* only and make sure the memory you have installed 'checks out'.
  4. StealthRider macrumors 65816


    Jan 23, 2002
    Yokosuka, Japan
    Make sure they aren't high density, buffered, ECC, PC66, etc...Blue and Whites are picky about memory, but most of the newer stuff that I've picked up has worked in the old machines my school has lying around. Just go grab a couple of 256 sticks for the SDR G4s and you should be fine.
  5. mhhack thread starter macrumors newbie

    Feb 21, 2006
    G3 memory chips

    Thanks to all of you who have given me some leads. The thing that is so weird is that the three 256mb sticks work together, as does the 128mb stick with any two of the 256mb sticks, and nothing seems to be slot specific. It's only when the four slots are filled that the G3 won't boot.
    I was able to run Dimm First Aid with the three 256mb sticks, and two of them are 8ns PC100-22, and one is 7.5ns PC100-333. All check out OK, except ther PC100-333 also says that the SPD data is old or incorrect , and that CL2 is not supported.

    Maybe all the memory has to be exactly the same, PC100-222, for all four slots to work together.

    Any other suggestions?
  6. RGunner macrumors 6502a


    Jul 3, 2002
    Midnight Sun
    Hey there

    The only other item I can add is this:

    Whatever you place in the first slot (is it J19?) will somewhat force the other chips to those specs (I have not confirmed this myself). So in theory place the 'slowest' 'oldest' in slot 1 (or j19 etc) and let the others conform to it.

    Does that make sense?

    Do post your question at www.macgurus.com I am sure someone there has more knowledge on this.
  7. Dane D. macrumors 6502a

    Apr 16, 2004
    No, the proper way is to load the fastest, largest chip in the first slot, closest to the CPU. I have mine set as follows; slot 1 - PC133-256MB, PC-100-256, PC-100-128MB, PC-66-64MB. You are correct in that slot 1 sets the timing. No other combo worked for me.
  8. RGunner macrumors 6502a


    Jul 3, 2002
    Midnight Sun
    Not going to argue

    Well I respectfully disagree, but the user should try it both ways.

    If slot 1 sets the timing, then by putting the best chip in slot 1 you are forcing the other chips to run at those timings, hence overclocking the slower chips.
  9. iPhil macrumors 68040


    The Ram slot 1 is always for the new Ram chip then the old slot1 chip will go to slot 2 then slot 2 old chip would go to slot 3 etc ..

    Thats the way i've used for the Windows boxes and this iMac that i'm typing on now ..

    If you wanna max out the B&W G3 then put 256MB x4 in any order since each ram stick is the same size in MB

    Hopefully i was clear enough for you :eek: :eek:

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